1. Field of the Invention
The present invention relates to reclosable plastic bags. This invention more particularly pertains to a fastener tape having reclosable fasteners thereon and adapted to be mounted in an opening of a reclosable bag.
2. Description of the Prior Art
Reclosable plastic bags having interlocking pressure-sealable profile fasteners are well known and have a variety of useful applications, such as the storage of household goods. The recent increase in consumer demand for reclosable bags has been coupled with a demand for higher quality profile fasteners in these bags. To meet these demands, manufacturers must develop cost effective and reliable methods of producing reclosable bags that are suitable for a consumer""s particular purpose.
Consumers prefer reclosable bags in which the reclosable opening is across the top of the bag. Until recently, however, most reclosable plastic bags were manufactured with the reclosable opening located along a vertical side of the bag, rather than across the top of the bag. Simply, it was easier for manufacturers using conventional equipment and processes to attach fasteners along the side of the bag than it was to attach fasteners across the top of the bag. Recent advances in manufacturing equipment and materials have allowed some manufacturers to produce reclosable bags with the reclosable openers across the top of the bag. For example, such equipment is available from AMI/Rec-Pro, Inc. in Atlanta, Ga., USA.
Typically, most commercially available reclosable plastic bags are formed of thermoplastic, such as polyethylene. An opening in the plastic bag is equipped with a plastic profile fastener which allows the plastic bag to be opened and resealed when accessing the contents of the plastic bag. These profiles include a male profile and a female profile configured to interlock and form a continuous closure when aligned and pressed together. Interlocked male and female profiles are commonly referred to, in the singular sense, as a profile fastener, zipper profile, or merely as a profile.
There is one type of extrusion process used to extrude materials for use at the top of a bag that is known as a flange zipper process. In such a process, the profile is extruded to form flanged portions, extending from the profile fastener. However, there are problems in sealing extruded, flanged profile directly to the walls of the plastic bag (referred to as the bag walls) due to the thickness of the flanged portions. Specifically, extruded, flanged profile has a limitation as to how thin the flanges can be integrally extruded. The extrusion process results in a flanged area having a thickness significantly greater than if a similar type profile was separately manufactured and attached to a separately manufactured intermediate layer.
As an alternative to attaching flange zipper profiles directly to the bag walls, the profile may only be attached to an intermediate layer of film. The intermediate layer with the attached profile is then attached to the bag walls. The combination of the profile and the intermediate layer is commonly referred to as xe2x80x9cfastener tape.xe2x80x9d The fastener tape and bag walls are suitably interconnected by generally known means, such as heat sealing, wherein the intermediate layer is sealed to the walls of the base material. The use of an intermediate layer permits the use of profiles that are made of a different material than the plastic bag walls. These different materials may be thermally incompatible. It is desirable to produce an intermediate layer in the thinnest manner possible in order to minimize the amount of heat necessary to attach the intermediate layer to the plastic bag. The intermediate layer is more effectively attached to a plastic bag with a minimal amount of heat, when the intermediate layer is in its thinnest form.
Excess heat in the manufacture of reclosable plastic bags promulgates defects. For example, if the intermediate layer or the profile comes into contact with excessive heat, the seal between the walls of the plastic bag and the intermediate layer may become damaged or the profile may become deformed. Such damage may be identified by an inoperable profile, wrinkles or creases in the walls of the plastic bag, or curls at the edges of the bag near the profile. Heat sealing is even more difficult when the walls of the bag are something other than polyethylene, for example polypropylene.
When manufacturing reclosable plastic bags with fastener tape, it is often desirable to include a peel seal between opposing portions of the intermediate layer. Such a peel seal assures that the integrity of the bag will be maintained until it is initially opened by the consumer by providing a hermetic seal.
In practice, however, it is has proven problematic to cost-effectively and consistently manufacture fastener tape with a peel seal. Typically in prior art fastener tapes, portions of the intermediate layer are coated with an adhesive. The intermediate layer is then folded so as to bring the adhesive bearing portions into an opposing relationship, after which the adhesive bearing portions are sealed together to form a peel seal. This method, however, is extremely complex and requires exacting control to ensure that the process is kept within acceptable parameters. Additionally, the adhesive tends to hold the ends of the fastener tape together, making the bag difficult to open. Further, it is often difficult to apply the adhesive and the adhesive can be very expensive.
In response to the realized inadequacies of known fastener tapes, it became clear that there is a need for a new type of fastener tape which facilitates the implementation of a peel seal.
Accordingly, an object of the present invention is to provide an improved fastener tape which facilitates the implementation of a peel seal.
Another object of the present invention is to provide a method of and apparatus for manufacturing the improved fastener tape.
Another object of the present invention is to provide a new method of using the improved fastener tape in the manufacture of reclosable plastic bags.
Yet another object of the present invention is to provide a new type of reclosable plastic bag which utilizes the improved fastener tape.
The foregoing objects are achieved by providing a fastener tape having an intermediate layer designed to enable the creation of a consistent peel seal.
In accordance with the present invention, the fastener tape includes an intermediate layer and a reclosable fastener profile thereon having a male profile interlockable with a female profile. The intermediate layer includes three layers of co-extruded plastic in the following configuration: not more than 4% EVA as the outer two layers and HDPE as the middle layer. The intermediate layer is folded so as to bring portions of the intermediate layer into an opposing relationship. These opposing portions are then sealed together by a pair of seal bars. By carefully controlling the sealing temperature, a consistent peel seal is created between the opposing portions of the intermediate layer.
The fastener tape is created through the use of delivery and applicator assemblies. The delivery assembly includes a plurality of rollers configured for delivering the intermediate layer to the applicator assembly. The tension of the intermediate layer between the rollers is controlled by a motorized drive roller. At least one of the plurality of rollers is fixed to the distal end of a pivoting arm. The proximal end of the arm is attached to an axis which passes through the delivery assembly to a cam. As the tension of the intermediate layer in the rollers increases and decreases, the arm and cam rotate. The rotation of the cam is detected and a signal is sent to the motorized roller to change the rate of speed of the intermediate layer through the rollers.
Also on the delivery assembly is a generally V-shaped panel member for folding the intermediate layer. The intermediate layer passes over a declined surface of the V-shaped panel member and over an apex to define a fold line in the intermediate layer. Before the folded intermediate layer is received by the applicator assembly, the profile fastener is inserted into the folded intermediate layer and oriented parallel to the machine direction of the intermediate layer. On the applicator assembly are a plurality of wheels having circumferential grooves sized for receiving the profile, and a pair of rotating belts. The wheels align the profile with the intermediate layer as the intermediate layer and profile are directed into two pairs of opposed sealing bars by the belts to form the fastener tape. The sealing bars of each set are moveable with respect to one another from a spaced clearance position into a clamping and sealing position. In the clamping and sealing position, the first set of sealing bars seal the profile to the intermediate layer and the second set of sealing bars seal opposing portions of the folded intermediate layer to one another to form a peel seal. In order to achieve the peel seal, the sealing temperature is carefully controlled by blowing ambient air from a manifold above the applicator assembly, bringing the belt temperature down from approximately 180xc2x0 F. to a narrow window of 85 to 100xc2x0 F.
After manufacture, the fastener tape may be used to make reclosable plastic bags. Generally speaking, when making plastic bags having reclosable zipper profiles, it is necessary to seal, or stomp, the ends of the profile to ensure that the ends of the profile do not come apart during use by the consumer. Such sealing or stomping, however, often requires expensive and complex modifications to the bag making machinery.
In accordance with the present invention, the lengths of fastener tape used in the manufacture of reclosable plastic bags may advantageously be provided with seals at their ends immediately above the profile which merge into the peel seal and which seal opposing portions of the intermediate layer to each other in a permanent fashion. These end seals, referred to as block seals, eliminate the need to stomp the ends of the zipper.
These block seals may be pre-applied to the fastener tape or may be applied during sealing of the fastener tape to the reclosable bag. In the latter case the block seals also seal the side folds of the plastic bag.
The foregoing has broadly outlined some of the more pertinent objects and features of the present invention. These should be considered to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or by modifying the disclosed embodiments. Accordingly, other objects and a more comprehensive understanding of the invention may be obtained by referring to the detailed description of the preferred embodiment taken in conjunction with the accompanying drawings, in addition to the scope of the invention defined by the claims.